Full Idea
Would any man, who is walking along, tread as willingly on another's gouty toes, whom he has no quarrel with, as on the hard flint and pavement?
Clarification
Gout is excrutiatingly painful and sensitive
Gist of Idea
No one would cause pain to a complete stranger who happened to be passing
Source
David Hume (Enquiry concerning Principles of Morals [1751], V.II.183)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.226
A Reaction
He is right that we empathise with the pain of others, and this is presumably one of the bases of morality. Animals lack sympathy for other animals.